Having determined the X-ray crystal structures of Glycera and lamprey hemoglobins at 2.5 angstrom units and 2.0 angstrom units respectively it is proposed to refine these structures both with and without ligands at 1.5 angstrom units resolution. The goal is to define as objectively and precisely as possible the structural changes that accompany the binding of ligands. In this way, details will be obtained about Perutz's "trigger" that are not obtainable from studies of tetrameric hemoglobins that provide lower resolution data than do these monomeric hemoglobins. It is planned to complete the development of the computer programs for the refinement of protein crystal structures that have been under development here, and to complete the establishment of the PDP 11/40 lab terminal to the CDC computing complex at Brookhaven. Crystal structure analyses have been initiated on earthworm hemoglobin, Limulus hemocyanin and its subunits and on Trout hemoglobins I and IV. A 70,000 Dalton subunit of Limulus hemocyanin has been crystallized. Six isomorphous heavy atom derivative crystals have been prepared. The derivative with Ziese's salt (K Pt Cl3 CH= CH2) provided an interpretable difference Patterson map, and signs for a centrosymmetric projection. Three different kinds of X-ray quality crystals of Trout hemoglobins I and IV have been grown.